This invention relates to guns using compressed gas to power a projectile, and more particularly, to a gun capable of powering a projectile by either air compressed by a hand pump mechanism or a compressed gas contained in a cartridge. The gun also has a switching mechanism operated by a user for switching between the hand pumping mechanism and the compressed gas cartridge. Thus, the present invention offers the user the versatility of propelling a projectile from a gun using either air compressed by a hand pump or compressed gas contained in a cartridge and offers this versatility by the simple actuating of a switch.
Guns have been provided with a hand pump to compress air to propel a projectile (such as a BB or pellet) in the past. For example, U.S. Pat. No. 3,802,408 describes a gun having a pump handle and pump mechanism for compressing air to propel a projectile. The pump handle is actuated by the gun's operator to compress the air. Guns have also been provide with compressed gas cartridges for propelling a projectile. For example, U.S. Pat. No. 4,344,410 describes a gun having a cartridge filled with compressed carbon dioxide to power a projectile.
U.S. Pat. Nos. 2,566,181 and 2,652,821 describe a gun powered by solid carbon dioxide disposed in a reservoir. The gun is also described as having an operating handle for actuating a piston in a cylinder to increase the pressure of the carbon dioxide by further compressing the carbon dioxide. These patents further state that it is also contemplated that it may be desirable to operate the gun in the event of failure of the supply of gaseous carbon dioxide and that this may be readily accomplished by removing the plug from the lower end of the reservoir whereupon the piston and the cylinder will act solely as a compressed air pump receiving air from the atmosphere through the reservoir and the passage and compressing this air in the firing reservoir.
U.S. Pat. No. 1,214,398 describes a gun having a flask containing air under pressure to propel a projectile. The patent states that a lever is raised to open a charging valve and the result being that high pressure air from the flask flows along an air line, through an outlet which is uncovered by a valve, and into a charging chamber. The charging valve is held open until the charge in the chamber drives a piston forward and compresses a cushion. When this occurs, the valve is drawn over the outlet and further admission of high pressure air is automatically cut off. The lever is then restored to its normal position. The patent further states that for manually increasing the air pressure in the discharge chamber, as for instance when the pressure in the flask begins to run low, an additional means is provided in the shape of a pump which may well be actuated at will. The patent states that when the operator grasps the grip and manipulates the lever, the piston is reciprocated within its cylinder, air is drawn in and forced out and flows along a line to the discharge chamber.